After just hearing the news, I imagine Kid being at a complete loss
of words. He'd be searching for a way to take her pain away and
bring her comfort. Kid would definitely remind her of the undying
love he has for her. Although he would have tremendous anger stirring
in his chest towards the deceased Wicks, I don't think he'd openly
display it. Instead, he would have focused his energy on supporting
Lou, and telling her how much he admires her strength and courage.

I think this is one area that the writers of the series really let us down by not letting us see firsthand Kid's reaction.
I think finiding out anyone laid hands on Lou would have ignited
a slow burning fury in his chest. If Wicks had not already been dead when
Lou told him, I think there would have been no stopping Kid from
killing him (remember Blood Money). However, to Lou he would have been a
picture of concern, and would have been more determined than ever
to protect her from harm. He would have been intent on proving to her it wasn't her fault, and he would have carried the secret to his grave.

I believe that when Lou was ready to tell Kid she knew that he would
be there to comfort her. He would do anything to help her get over
what wicks had done to her in the past and make sure that nothing
like that would ever happen to her again. Since wicks was already
killed Kid didn't have to kill him. Thats what he felt like doing
when he found out what he did to the woman he loved. Kid swore from
that moment on he would always be there for her no matter what happened
to them in the future. He told her much he loved her and would give
up his own life to make sure she was safe from any harm. In return
she told him how much she loved him. They just held each other tightly
as they watched the sun set. Lou looked in Kid's eyes and knew she would always be safe.

I think Kid would have felt angry and to a certain extent, helpless
because he would want to punish Wicks for what he did to Lou but
it was too late when he found out.
It would also make him more determined than ever to keep Lou by
his side so he could protect her in the future. He must have understood
how much Lou loved and trusted him when she shared her past with him.
It really strengthened the bond between them and helped them both
realise how much they need each others love and support.